ANTHOCYANS 341 



The anthocyans are glucosides and are converted by hydrolysis with acids 

 into glucose and anthocyanidins. The anthocyanidins are pigments like the 

 anthocyans, but they are soluble in amyl alcohol. The glucosidic character 

 of the anthocyans can be easily demonstrated : 



1-2 gm. of blossom are rubbed with 5-10 parts of sand and a few c.c. 

 of dilute sulphuric acid and a small quantity of alcohol ; some talc is added 

 to help filtration. The mass is shaken with amyl alcohol. The emulsion 

 which is formed may be broken by pouring upon a wet filter and then pour- 

 ing the material upon a dry filter. On washing the amyl alcohol with water or 

 sodium acetate solution it will not be coloured or only faintly. Another 

 portion of the blossom may be heated for half an hour with the acid and 

 treated in the same way. The amyl alcohol will be pigmented. 



The same can be observed with '05-1 gm. of anthocyan, but the 

 filtration is not necessary. 



The following anthocyans have been investigated : 



(1) Cornflower and rose 



cyanin -> 2 x glucose + cyanidin. 



(2) Cranberry 

 idain->galactose + cyanidin. 



(3) Blue grapes 



oenin - glucose + oenidin. 



(4) Whortle berry and Althcea rosea 

 myrtillin -> glucose + myrtillidin. 



(5) Larkspur 



delphinin -> 2 mol. glucose + 2 mol. /-oxybenzoic acid + delphinidin 



(6) Pelargonium 



pelargonin-^ 2 x glucose + pelargonidin. 



The anthocyanidins are closely related to the anthoxanthins : 

 Cyanidin is isomeric with luteolin, caempferol and fisetin. 

 Pelargonidin is isomeric with apigenin and galangin. 

 Delphinidin is isomeric with quercetin and morin. 



Cyanidin on heating with alkali gives phloroglucinol and protocatechuic acid. 

 Pelargonidin on heating with alkali gives phloroglucinol and p-hydroxy- 



benzoic acid. 



Delphinidin on heating with alkali gives phloroglucinol and gallic acid. 

 The constitution of these anthocyanidins is probably : 



OH nor Y ii c >OH 



CH3 



OH OH 



Delphinidin. Oenidin. 



Though these compounds are so closely related to the anthoxanthins, the 

 transformation of the one group into the other is not easily effected, but 

 quercitin on reduction has been converted into cyanidin. It is very likely 

 that the two groups of compounds are converted into one another by oxidative 

 and reducing enzymes. 



